[PATCH v1 2/5] KVM: s390: vsie: Fix delivery of addressing exceptions

David Hildenbrand
2020-04-02T18:48:34Z

Whenever we get an -EFAULT, we failed to read in guest 2 physical
address space. Such addressing exceptions are reported via a program
intercept to the nested hypervisor.

We faked the intercept, we have to return to guest 2. Instead, right
now we would be returning -EFAULT from the intercept handler, eventually
crashing the VM.

Addressing exceptions can only happen if the g2->g3 page tables
reference invalid g2 addresses (say, either a table or the final page is
not accessible - so something that basically never happens in sane
environments.

Identified by manual code inspection.

Fixes: a3508fbe9dc6 ("KVM: s390: vsie: initial support for nested virtualization")
Cc: <stable@vger.kernel.org> # v4.8+
Signed-off-by: David Hildenbrand <david@redhat.com>
---
arch/s390/kvm/vsie.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 076090f9e666..4f6c22d72072 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -1202,6 +1202,7 @@ static int vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
scb_s->iprcc = PGM_ADDRESSING;
scb_s->pgmilc = 4;
scb_s->gpsw.addr = __rewind_psw(scb_s->gpsw, 4);
+ rc = 1;
}
return rc;
}
--
2.25.1